Node.js Express Project Structure

What is Express Project Structure in Node.js?

A maintainable Express project separates routing, business logic and data access. Routes describe URLs, controllers coordinate, services hold the logic, and models talk to the database.

Express Project Structure example

src/
├── index.js            # bootstrap: config, db, app.listen
├── app.js              # express app, middleware, route mounting
├── config/             # env parsing, database connection
├── routes/             # jobs.routes.js — URLs only
├── controllers/        # jobs.controller.js — req/res handling
├── services/           # jobs.service.js — business logic, no req/res
├── models/             # jobs.model.js — schema and queries
├── middleware/         # auth, validate, errorHandler
└── utils/              # logger, helpers

Key points to remember

• Services must not touch req or res — that keeps them testable and reusable.
• Separating app.js from index.js lets tests import the app without starting a server.
• Keep each layer thin; a controller that is fifty lines is doing service work.

Common mistakes with Express Project Structure

• Database queries written directly inside route handlers.
• Business logic in controllers, which makes it impossible to reuse from a job or CLI.